Methods of removing fines and coarse particles from oil sand tailings, and related mixtures

ABSTRACT

A method of removing fines and coarse particles from tailings comprises forming a slurry comprising water and oil sands and separating bitumen from tailings comprising fines and coarse particles. Functionalized nanoparticles each comprising a core of carbon nitride and functionalized with one or more exposed cationic groups are mixed with the tailings. The functionalized nanoparticles and the fines interact to form agglomerates comprising the functionalized nanoparticles and the fines attached to the one or more exposed cationic groups. The agglomerates are removed from the tailings to form an aqueous solution having suspended therein fewer fines and coarse particles than are suspended within the tailings.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.15/002,130, filed Jan. 20, 2016, now U.S. Pat. No. 9,856,158, issuedJan. 2, 2018 the disclosure of which is hereby incorporated herein inits entirety by this reference.

TECHNICAL FIELD

Embodiments of the disclosure relate generally to methods of removingfines and coarse particles from tailings with nanoparticlesfunctionalized with one or more terminal cationic functional groups.More particularly, embodiments of the disclosure relate to methods ofagglomerating fines and coarse particles that are suspended in tailingswith functionalized carbon nitride nanoparticles.

BACKGROUND

Oil sands are known to contain hydrocarbons known as bitumen trappedbetween individual grains of the oil sands. Water surrounding the grainscontains very fine clay particles, fine sand, and silt (referred to inthe art as “fines”). The bitumen from the oil sands may be recovered byforming a slurry including the oil sands dispersed in an aqueoussolution (e.g., water) that may include caustic (e.g., NaOH) in additionto the water. The slurry is fed into a primary separation vessel (PSV)(e.g., a floatation cell) where the oil sands are aerated. Air isbubbled through a bottom portion of the PSV, such as with a sparger, andaerated bitumen rises to the surface to form a froth that overflows thePSV and is recovered for further treatment. Eventually, the recoveredbitumen may be upgraded to crude oil, such as by fluid coking, hydroprocessing, hydro treating, and reblending.

Gravitational forces cause the sand grains to sink and concentrate atthe bottom of the PSV. Middlings, a watery mixture containing suspendedfines and bitumen, extend between the froth and the sand layers. Theunderflow and the middlings are frequently combined and processed in asecondary floatation process (known as a Tailings Oil Recovery (TOR)vessel) to recover any bitumen that may remain in the tailings or in themiddlings. The middlings and an underflow from the TOR may be furtherprocessed to recover any unrecovered bitumen, or may be discarded astailings. The middlings and the underflow from the TOR vessel mayeventually be sent to a tailings pond. In some instances, the underflowcontains mainly coarse sands, which may be pumped to a tailingsdeposition area.

However, the middlings may include coarse sands, mineral fines, anddissolved metals (e.g., mercury, arsenic, etc.) and are, therefore, notsuitable for direct discharge into the environment (e.g., rivers). Thus,the middlings are frequently discharged into a tailings pond where thefines are allowed to settle under gravitational forces. Unfortunately,the fines remain stable in the tailings and may take months to severalyears to settle. This excessive duration presents issues in the recoveryof bitumen from oil sands.

BRIEF SUMMARY

Embodiments disclosed herein include methods of removing fines anddissolved solids from tailings. For example, in accordance with oneembodiment, a method of removing fines and coarse particles fromtailings formed during recovery of bitumen from oil sands comprisesforming a slurry comprising water and oil sands, separating bitumen fromtailings in at least one of a primary separation vessel or a secondaryseparation vessel, the tailings comprising a solution having fines andcoarse particles suspended therein, mixing functionalized nanoparticleswith the tailings, the functionalized nanoparticles each comprising acore of carbon nitride and functionalized with one or more terminalcationic groups, forming agglomerates comprising the functionalizednanoparticles and at least the fines attached to the one or moreterminal cationic groups, and removing the agglomerates from thetailings to form an aqueous solution having suspended therein fewerfines and coarse particles than are suspended within the tailings.

In additional embodiments, a method of removing fines from tailingscomprises mixing functionalized nanoparticles each comprising at leastone exposed amine functional group on surfaces of a carbon nitride corewith tailings including negatively charged fine particles to form amixture, attaching the negatively charged fine particles to the at leastone exposed amine functional group to form agglomerations of the fineparticles attached to the functionalized nanoparticles, theagglomerations having a larger diameter than each of the negativelycharged fine particles, and separating the agglomerations from thetailings to form a substantially clarified aqueous solution having fewerfines suspended therein than are suspended in the tailings.

In further embodiments, a method of separating fines and dissolvedmetals from tailings comprises forming a mixture comprising carbonnitride nanoparticles functionalized with one or more terminal cationicgroups and tailings including a plurality of fines, coarse particles,and dissolved metals suspended therein, binding at least some of thedissolved metals with a core of the carbon nitride nanoparticles,attaching at least some of the fines of the plurality of fines to theone or more terminal cationic groups to form agglomerations of thecarbon nitride nanoparticles, bound dissolved metals, and fines, andsettling the agglomerations from the tailings to form an aqueoussolution having fewer fines, coarse particles, and dissolved metalssuspended therein than are suspended in the tailings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified flow diagram depicting a method of removing finesfrom tailings, in accordance with embodiments of the disclosure; and

FIG. 2 is a simplified schematic of an embodiment of a functionalizednanoparticle, in accordance with embodiments of the disclosure.

DETAILED DESCRIPTION

Illustrations presented herein are not meant to be actual views of anyparticular material, component, or system, but are merely idealizedrepresentations that are employed to describe embodiments of thedisclosure.

The following description provides specific details, such as materialtypes, compositions, material thicknesses, and processing conditions inorder to provide a thorough description of embodiments of thedisclosure. However, a person of ordinary skill in the art willunderstand that the embodiments of the disclosure may be practicedwithout employing these specific details. Indeed, the embodiments of thedisclosure may be practiced in conjunction with conventional techniquesemployed in the industry. In addition, the description provided belowdoes not form a complete process flow for removing fines, coarse solids,and dissolved metals from tailings or a tailings pond. Only thoseprocess acts and structures necessary to understand the embodiments ofthe disclosure are described in detail below. A person of ordinary skillin the art will understand that some process components (e.g.,pipelines, line filters, valves, temperature detectors, pH meters, flowdetectors, pressure detectors, and the like) are inherently disclosedherein and that adding various conventional process components and actswould be in accord with the disclosure. Additional acts or materials totreat tailings or a tailings pond may be performed by conventionaltechniques.

As used herein, the term “fines” means and includes solids such as veryfine clay particles, fine sand, and silt that have a diameter less thanabout 1 μm, such as less than about 500 nm, less than about 100 nm, orless than about 10 nm. As used herein, the term “coarse particle” meansand includes particles that have a diameter larger than a diameter offines.

As used herein, the term “tailings” means and includes a solutionincluding fines, coarse particles, or a combination thereof suspended ina substantially aqueous solution.

Methods and functionalized nanoparticles as disclosed herein may be usedfor improving fines settling and dissolved metals removal in minetailings, such as in tailings and tailings ponds. For example, coarsesands as well as fines in tailings that result from mining and bitumenextraction from oil sands may be removed from the tailings. In someembodiments, functionalized nanoparticles are mixed with the tailings toform agglomerations of the functionalized nanoparticles and the fines,coarse particles, and dissolved metals. In some embodiments, water fromthe tailings may be reused in the bitumen extraction process (e.g.,bitumen floatation). The reused water may be at an elevated temperatureand may be used in the floatation process without reheating the purifiedwater. Accordingly, use of the functionalized nanoparticles according tomethods disclosed herein may reduce an amount of tailings formed duringoil recovery processes (e.g., bitumen extraction from oil sands).

FIG. 1 is a simplified block diagram illustrating a method 100 ofrecovering bitumen from oil sands and removing fines and coarseparticles from the tailings using functionalized nanoparticles accordingto an embodiment of the disclosure. The method 100 includes act 102 thatincludes mixing an aqueous solution with oil sands; act 104 thatincludes removing bitumen from oil sands in one or more primaryseparation vessels (PSVs) (e.g., a primary floatation vessel); act 106including treating middlings and an underflow from the PSV in one ormore secondary recovery vessels (e.g., a secondary floatation vessel);act 108 including adding functionalized nanoparticles to the tailingsfrom one or more of the PSVs, the secondary recovery vessels, or atailings pond to separate fines, coarse particles, and dissolved metalsfrom the tailings and form a substantially purified aqueous solution andagglomerations of the fines, coarse particles, and dissolved metals; act110 including removing the agglomerations from the substantiallypurified aqueous solution; and act 112 including recycling at least aportion of the aqueous solution to one or more of a PSV or a secondaryrecovery vessel.

Act 102 includes mixing an aqueous solution with oil sands to form aslurry. In some embodiments, one or more additives to facilitateseparation of bitumen from the oil sands may be added to the slurry. Insome such embodiments, sodium hydroxide may be added to the slurry tofurther improve bitumen recovery.

Act 104 may include separating bitumen from the oil sands. In someembodiments, the slurry may be added to a primary separation vessel(e.g., a primary floatation vessel) and air or another gas may besparged or otherwise bubbled through a portion of the vessel to aerateand float the bitumen in a floatation process. Since the bitumen ishydrophobic, it may be attracted to surfaces of the bubbles formedduring floatation. Accordingly, the aerated bitumen may separate fromthe oil sands and rise to a top of the PSV, forming a froth, during thefloatation process. In some embodiments, the froth spills over the topof the PSV or is skimmed from the surface of aerated fluid and isfurther processed to recover the bitumen from the froth.

Act 106 includes removing an underflow (e.g., tailings) and middlingsfrom the one or more PSVs and treating the tailings and middlings in oneor more secondary recovery vessels to recover additional bitumentherefrom. The one or more second recovery vessels may include one ormore of Tailings Oil Recovery (TOR) vessels, stationary settlingvessels, floatation cells, Jameson cells, or combinations thereof. Insome embodiments, bitumen recovered in the secondary recovery vessel isrecycled back to the PSV, where it may be further processed andrecovered in the froth.

Tailings from one or more PSVs, one or more secondary recovery vessels,or a combination thereof may include fines, coarse particles, anddissolved metals suspended therein. In some embodiments, a size (e.g., adiameter) of suspended particles within the tailings may exhibit abimodal distribution. By way of nonlimiting example, the suspendedparticles may include fines that may be spherical having a size betweenabout 100 nm and about 500 nm, such as between about 100 nm and about300 nm, or between about 150 nm and about 250 nm. The suspendedparticles may also include coarse particles or grains that may have asize between about 500 nm and about 1500 nm.

The suspended particles in the tailings may exhibit a zeta potentialsuch that the fines remain substantially stable while suspended insolution and do not exhibit a tendency to flocculate. In someembodiments, the zeta potential of the suspended particles may bebetween, for example, −10.0 mV and about −30.0 mV, such as between about−15.0 mV and about −25.0 mV. In some embodiments, the zeta potential ofthe fines is about −25.0 mV.

The fines and coarse particles may be sized and shaped such that theyremain dispersed and suspended in the tailings rather than settling dueto gravitational forces. In some embodiments, the tailings are containedand stored in a tailings pond where the tailings are allowed to settlevia gravitational forces. However, settling of the fines in a tailingspond may take months or even years to occur.

Accordingly, act 108 includes adding functionalized nanoparticles to thetailings or a tailings pond to separate the fines, coarse particles, anddissolved metals from the tailings. Functionalized nanoparticlesformulated and configured to interact with one or more of the fines, thecoarse particles, and the dissolved metals in the tailings may be mixedwith the tailings. Responsive to interacting with the functionalizednanoparticles, one or more of the fines, coarse particles, or thedissolved metals may form a complex with the functionalizednanoparticles and agglomerate and settle under gravitational forces. Asubstantially purified aqueous solution is formed as the fines, coarseparticles, and dissolved metals agglomerate to the functionalizednanoparticles and settle out of solution.

In some embodiments, the tailings are disposed in a tank and thefunctionalized nanoparticles are added to the tank. The tank may includeone or more mixers configured to disperse the functionalizednanoparticles within the tailings and provide intimate contact betweenthe functionalized nanoparticles and the tailings. In other embodiments,the functionalized nanoparticles are dispersed within a tailings pond.

The functionalized nanoparticles may be generally spherical in shape. Insome embodiments, the functionalized nanoparticles have a size betweenabout 5 nm and about 100 nm, such as between about 5 nm and about 50 nm,between about 10 nm and about 25 nm, or between about 10 nm and about 20nm.

The functionalized nanoparticles may be provided at a concentration ofabout 10 ppm and about 1,000 ppm, such as between about 10 ppm and about500 ppm, between about 25 ppm and about 350 ppm, between about 50 ppmand about 250 ppm, or between about 100 ppm and about 150 ppm. In someembodiments, the functionalized nanoparticles are provided at aconcentration between about 150 ppm and about 350 ppm. In someembodiments, the functionalized nanoparticles may be provided such thatthe tailings include about one functionalized nanoparticle for aboutevery two fine particles.

FIG. 2 illustrates a simplified schematic of an embodiment of afunctionalized nanoparticle 200 that may be mixed with the tailings. Thefunctionalized nanoparticle 200 may include a core 202 and one or morefunctional groups 204 attached to a surface 206 thereof. The core 202may include carbon nitride (e.g., C₃N₄), boron carbon nitride, silica,alumina, zirconia, magnesium oxide, nanodiamonds (e.g., carbonnanodiamonds), graphene, graphene oxide, graphite (e.g., nanographite),onion-like carbon structures (e.g., a “bucky onion”), carbon nanotubes(e.g., single-walled carbon nanotubes (SWCNTs), multi-walled carbonnanotubes (MWCNTs), and combinations thereof), fullerenes, metal oxides(e.g., oxides of one or more of iron, titanium, tin, lead, ruthenium,nickel, cobalt, etc.), metal nitrides (e.g., nitrides of one or more ofiron, titanium, tin, lead, ruthenium, nickel, cobalt, etc.), metalcarbides (e.g., carbides of one or more of iron, titanium, tin, lead,ruthenium, nickel, cobalt, etc.), metal phosphates (e.g., phosphates ofone or more of iron, titanium, tin, lead, ruthenium, nickel, cobalt,etc.), metal sulfides (e.g., sulfides of one or more of iron, titanium,tin, lead, ruthenium, nickel, or cobalt), metalloid oxides (e.g., oxidesof one or more of germanium, aluminum, boron, silicon, etc.), metalloidnitrides (e.g., nitrides of one or more of germanium, aluminum, boron,silicon, etc.), metalloid carbides (e.g., carbides of one or more ofgermanium, aluminum, boron, silicon, etc.), metalloid phosphates (e.g.,phosphates of one or more of germanium, aluminum, boron, silicon, etc.),metalloid sulfides (e.g., sulfides of one or more of germanium,aluminum, boron, silicon, etc.), or combinations thereof. The core 202may be generally spherical in shape and may have an average particlediameter of between about 5 nm and about 100 nm, such as between about 5nm and about 50 nm, between about 10 nm and about 25 nm, or betweenabout 10 nm and about 20 nm.

In some embodiments, the core 202 comprises carbon nitride. The carbonnitride may include a C₃N₄ polymer. The C₃N₄ may be an amorphous carbonnitride or a graphitic carbon nitride. In one embodiment, the C₃N₄structure is graphitic carbon nitride having a generally sphericalshape. Generally, the carbon nitride material may have a chemicalstructure as shown below, where nitrogen atoms form bridges betweenadjacent triazine structures.

The carbon nitride of the C₃N₄ carbon nitride structure may includes-triazine rings (i.e., 1,3,5-triazine) bridged together by nitrogenatoms between adjacent triazine rings. The geometry of the C₃N₄ carbonnitride structure may be substantially spherical, similar tobuckminsterfullerene structures. In some embodiments, the C₃N₄ structuremay exhibit a multi-walled structure having a cage-like structure.Adjacent walls of the multi-walled structure may be separated by betweenabout 3 Å and about 4 Å. In some embodiments, the distance betweenadjacent walls of the multi-walled structures may be about 3.415 Å. Insome embodiments, the core 202 comprises a generally spherical shapewith a hollow center and the carbon nitride defined surfaces of thespherical shape.

In some embodiments, the core 202 may be sized, shaped, and configuredto bind contaminants in the tailings, such as the dissolved metals. Byway of nonlimiting example, the core 202 may comprise carbon nitride.The carbon nitride structure (e.g., a graphitic carbon nitridestructure) may inherently include vacancies (e.g., voids) that act assites for binding metallic cations dispersed in the tailings. Forexample, the carbon nitride may bind metal cations in the vacancies thatare inherently formed in a middle portion of triangular shaped openingsformed by nitrogen atoms bridged by adjacent triazine rings. In someembodiments, the cations may bind to an outer wall or layer of the core202. By way of nonlimiting example, the core 202 may be formulated andconfigured to bind one or more of dissolved metals such as lead (Pb²⁺,Pb⁴⁺), mercury (Hg₂ ²⁺, Hg²⁺), arsenic (As²⁺, As³⁺, As⁵⁺), nickel (Ni²⁺,Ni⁴⁺), vanadium (V²⁻, V³⁺, V⁴⁺, V⁵⁺), chromium (Cr²⁺, Cr³⁺), cadmium(Cd²⁻), cobalt (Co²⁺, Co³⁺), or other heavy metal cations that aredissolved in the tailings.

The one or more functional groups 204 may be cationic and may includeone or more cationic groups. In some embodiments, the cationic groupsmay be incorporated into the functional groups 204 and a positive chargethereof may not be substantially shielded from other portions of thefunctional groups 204. In other embodiments, the cationic groups may beterminal (e.g., exposed). The exposed cationic groups may be configuredto interact with the suspended fines and coarse particles in thetailings. The functional groups 204 may include one or moresubstantially linear functional groups 208 and one or more substantiallydendritic (e.g., branched) functional groups 210. In some embodiments,the dendritic functional groups 210 may include a branched structureattached to the surface 206 of the functionalized nanoparticle 200,wherein one or more of the branches are terminated by at least oneterminal cationic group.

The exposed cationic groups may include positively charged nitrogen,phosphorus, sulfur, or combinations thereof in a heterocyclic compoundthat may include a 5-membered ring or a 6-membered ring. In someembodiments, the exposed cationic groups may include one or more of anamine group (e.g., —NH₂, —NRH, —NR₂, where R may comprise similar ordifferent organic groups or hydrogen), a guanidine group, a bi-guanidegroup, guanidine derivatives, an imidazole group, a pyrazole group, apyridine group, a piperidine group, a pyrrolidine group, a morpholinegroup, a quinolone group, an isoquinoline group, an indole group, athiazole group, a benzothiazole group, a quaternary ammonium group, aphosphonium group (e.g., a quaternary phosphonium group), a sulfoniumgroup (e.g., a tertiary sulfonium group), a guanidinium group, abi-guanidinium group, an imidazolium group, a pyrazolium group, apyridinium group, a piperidinium group, a pyrrolidinium group, amorpholinium group, a quinolinium group, an isoquinolinium group, anindolium group, a thiazolium group, a benzothiazolium group, acyclopropenylium group, an amide group (e.g., one or more of an organicamide, a sulfonamide, or a phosphoramide), polyethyleneimine groups,derivatives thereof, or combinations thereof. In some embodiments, thefunctional groups 204 may be amine terminated, phosphonium terminated,sulfonium terminated, guanidinium terminated, bi-guanidinium terminated,imidazolium terminated, pyrazolium terminated, pyridinium terminated,piperidinium terminated, pyrrolidinium terminated, morpholiniumterminated, quinolinium terminated, isoquinolinium terminated, indoliumterminated, thiazolium terminated, benzothiazolium terminated,cyclopropenylium terminated, amide terminated, or combinations thereof.The one or more terminal cationic groups may be attached to the surface206 of the functionalized nanoparticle 200 with, for example, a—C(═O)—R— linking group that may include one or more additional cationicfunctional groups. By way of nonlimiting example, the functional group204 may include one or more exposed terminal amine groups attached tothe core 202 via, for example, a —C(═O)—R(—O—CH₂CH₂—)_(n), group.

In some embodiments, at least some of the functionalized nanoparticles200 may include terminal amine groups, and at least some of thefunctionalized nanoparticles 200 may include one or more of terminalphosphonium, terminal sulfonium, terminal guanidinium, terminalbi-guanidinium, terminal imidazolium, terminal pyrazolium, terminalpyridinium, terminal piperidinium, terminal pyrrolidinium, terminalmorpholinium, terminal quinolinium, terminal isoquinolinium, terminalindolium, terminal thiazolium, terminal benzothiazolium, terminalcyclopropenylium, terminal amide groups, derivatives thereof, orcombinations thereof.

Where the functionalized nanoparticles 200 comprise terminal aminegroups, the terminal amine group may be one or more of primary amines(NH₂—R₁), secondary amines (NH—R₁—R₂), tertiary amines (N—R₁—R₂—R₃), orcombinations thereof, wherein R₁, R₂, and R₃ each comprise one or morefunctional groups that may include an alkyl group, an alkenyl group, analkynyl group, a hydroxyl group, an organohalide, a carbonyl group, anorganosulfur group, a carboxyl group, an ester group, an ether group, anepoxy group, a phenolic group, another amine group, a polyamine group,or combinations thereof.

The functionalized nanoparticles 200 may exhibit a zeta potential suchthat functionalized nanoparticles 200 remain suspended in solution priorto be mixed with the tailings. In some embodiments, the functionalizednanoparticles 200 may be stable when dispersed in the tailings and maybe suspended therein. The functionalized nanoparticles 200 may exhibit azeta potential between about +10.0 mV and about +30 mV, such as betweenabout +15.0 mV and about +25.0 mV. In some embodiments, the zetapotential of the fines is about +25.0 mV, such as about +26.4 mV. Anabsolute value of the zeta potential of the functionalized nanoparticles200 may be equal to approximately an absolute value of the zetapotential of the fines dispersed in the tailings stream. In someembodiments, the zeta potential of the functionalized nanoparticles 200may be positive while the zeta potential of the fines is negative.

Without wishing to be bound by any particular theory, it is believedthat the negatively charged fines and coarse particles of the tailingsinteract with the exposed cationic groups of the functionalizednanoparticles 200, increasing a tendency of the fines and coarseparticles to agglomerate with the functionalized nanoparticles 200. Thefunctionalized nanoparticles 200 neutralize surface charges of the finesand coarse particles, destabilizing the fines and coarse particles andallowing them to form agglomerations having a larger size thanindividual fines or coarse particles that are suspended in the tailings.The agglomerations including the functionalized nanoparticles 200, thefines, and coarse particles have a larger size than the individualfines, increasing a potential for the fines to settle to a bottom of thetailings ponds or tank. In addition, the agglomerations exhibit a zetapotential of about 0 mV, meaning that the agglomerations are not stableas a suspension, but rather, that the agglomerations are more stablewhen settled. Thus, the agglomerations can be more easily removed fromthe tailings than the individual fines or coarse particles.

In some embodiments, where the functionalized nanoparticles 200 includea carbon nitride core 202, interaction between metallic cations (andprotons) and the carbon nitride core 202 may increase a scavengingability of the cationic functional groups 204 of the functionalizednanoparticles 200. Without wishing to be bound by any particular theory,it is believed that metallic cations and protons interact with andattach to one of an outer layer or an inner layer of a multi-walledcarbon nitride core 202. Accordingly, the core 202 may exhibit apositive charge due to the attached metallic cations and protons. Due tothe positive charge exhibited by the core 202, the cationic terminalgroups may be repelled by the core 202, causing the functional groups204 to extend radially from the core 202. Thus, the functional groups204 may exhibit an increased scavenging ability since the sweep of thefunctionalized nanoparticles 200 is increased by the repulsion of theterminal cationic groups from the positively charged core 202. Furtherstill, because the core 202 may exhibit a substantially large positivecharge, negatively charged fines and coarse particles in the tailingsmay be attracted to the core in addition to the terminal cationic groupsof the functional groups 204. Accordingly, the functionalizednanoparticles 200 may be formulated and configured to bind dissolvedmetallic cations (e.g., cations of one or more of lead, mercury,arsenic, nickel, vanadium, chromium, cadmium, cobalt, zinc, copper,iron, manganese, molybdenum, titanium, or combinations thereof) as wellas fines and coarse solids that are suspended in the tailings.

In some embodiments, the functionalized nanoparticles 200 may beprovided as a colloidal suspension of functionalized nanoparticles 200including a carbon nitride core 202 and amine terminated functionalgroups 204. The colloidal suspension may be stabilized with one or moresurfactants configured to stabilize the suspension and prevent thefunctionalized nanoparticles 200 from agglomerating and settling. Thecolloidal suspension may exhibit a zeta potential of about +20 mV andmay include between about 0.5 weight percent (0.5 wt. %) and about 5weight percent functionalized nanoparticles 200, such as between about0.5 weight percent and about 3 weight percent, or between about 1.0weight percent and about 2.0 weight percent functionalized nanoparticles200. In some embodiments, the colloidal suspension includes about 1.0weight percent carbon nitride nanoparticles. In additional embodiments,the colloidal suspension also includes silica nanoparticlesfunctionalized with one or more functional groups having a terminalcationic functionalization (e.g., an amine termination).

In some such embodiments, the functionalized nanoparticles 200 may havea size between about 15 nm and about 25 nm, such as about 20 nm. Thecolloidal suspension including functionalized nanoparticles 200 withamine terminated functional groups 204 may be added to the tailings at aconcentration such that the resulting mixture of the tailings and thecolloidal suspension includes between about 10 ppm and about 1000 ppm ofthe functional nanoparticles 200. In some embodiments, the tailingsinclude between about 50 ppm and about 350 ppm of the functionalizednanoparticles.

In yet other embodiments, the functionalized nanoparticles 200 may beprovided to the tailings as a colloidal suspension stabilized in anacidic solution. The acid may include hydrofluoric acid, although thedisclosure is not so limited and the acid may include, for example,hydrofluoric acid or another acid. The colloidal suspension may exhibita pH between about 4.0 and about 6.0, such as between about 4.5 andabout 5.5. The functionalized nanoparticles 200 may exhibit a zetapotential greater than about +40 mV, such as about +42 mV and may havean average diameter of about 40 nm.

In other embodiments, the functionalized nanoparticles 200 may beprovided to the tailings as a powder. In some such embodiments, thefunctionalized nanoparticles 200 may comprise amine terminated carbonnitride powder. The amine terminated carbon nitride powder may exhibit azeta potential of about +10 mV and may have an average diameter betweenabout 10 nm and about 20 nm. The carbon nitride powder may be addeddirectly to the tailings. In some embodiments, a powder comprising amineterminated silica nanoparticles may further be added to the tailings.

In some embodiments, a flocculent may be added to the tailings. Theflocculent may include a high molecular weight anionic polyacrylamineflocculent, such as those sold under the tradename of Magnafloc® by BASFof Ludwigshafen, Germany. The flocculent may be formulated andconfigured to neutralize a surface charge of the suspended fines andcoarse particles and reduce a stability of the suspension. However, theflocculent may undesirably increase a viscosity of the tailings. Theincreased viscosity may reduce a settling rate of the fines.Accordingly, in some embodiments, the functionalized nanoparticles 200are added to the tailings to agglomerate the fines prior to addition ofthe flocculent. After addition of the functionalized nanoparticles 200,the flocculent may be added to the tailings to neutralize surfacecharges of the fines and reduce a stability of any suspended fines orcoarse particles. The flocculent may be added to the tailings such thatthe flocculent constitutes between about 50 ppm and about 350 ppm of thetailings after addition thereof.

In yet other embodiments, the tailings may be treated with a combinationof the functionalized nanoparticles 200 and a coagulant. The coagulantmay include a cationic polymer, such as, for example, poly diallyldimethylammonium chloride (polyDADMAC). The coagulant may enhanceprecipitation of the fines and coarse particles in the tailings. Themixture of the functionalized nanoparticles 200 and the coagulant mayenhance settling more than adding only one of the functionalizednanoparticles 200 or the coagulant. In some embodiments, between about50 ppm and about 350 ppm of the cationic polymer, such as between about50 ppm and about 300 ppm, or between about 100 ppm and about 200 ppm isadded to the tailings.

In some embodiments, the cationic polymer is mixed with the tailingsprior to mixing the functionalized nanoparticles 200 with the tailings.Addition of the functionalized nanoparticles 200 to the tailings aftermixing the tailings with the cationic polymer may increase a rate offines settling. In some embodiments, the fines in the tailings may besettled in a period less than about thirty minutes, such as less thanabout twenty minutes.

After addition of the functionalized nanoparticles 200 to the tailings,the mixture may be mixed to substantially disperse the functionalizednanoparticles 200 within the tailings and provide sufficient contactbetween the fines, coarse particles, and dissolved metals dispersed inthe tailings and the functionalized nanoparticles.

After addition of the functionalized nanoparticles 200 to the tailings,functionalized nanoparticles 200 may form agglomerations with the fines,coarse particles, and dissolved metals of the tailings. In someembodiments, the agglomerations may have an average diameter at leastabout five times greater than an average diameter of the coarseparticles. In some embodiments, the agglomerations may have an averagediameter at least about ten times greater than an average diameter ofthe coarse particles. The agglomerations may settle to a lower portionof the tailings. Separation of the agglomerations from the tailings mayform an aqueous solution having fewer fines and coarse particlessuspended therein than are suspended in the tailings. In someembodiments, the aqueous solution may also have less dissolved metalstherein than are dissolved in the tailings. In some embodiments, theaqueous solution may be substantially free of fines, coarse solids, anddissolved metals. The aqueous solution may exhibit an improved clarity(e.g., such as determined by turbidity) than the tailings.

With reference again to FIG. 1, act 110 includes removing theagglomerations from the substantially purified aqueous solution. In someembodiments, the agglomerations are transported to a solids treatment ora solids storage facility.

Act 112 may include recycling at least a portion of the substantiallypurified aqueous solution having fewer fines suspended therein than aresuspended within the tailings to one or more of the PSVs or thesecondary recovery vessels. In some embodiments, the aqueous solutionmay have a temperature equal to about a temperature of the aqueoussolution used at act 102 to form the slurry, such as between about 50°C. and about 80° C. Accordingly, the treated aqueous solution may berecycled and used at act 102 without heating the treated aqueoussolution to processing temperatures of the oil sand slurry. In otherembodiments, the aqueous solution may free of environmental toxins andmay be suitable to be deposited into the environment.

Compared to commercially available methods and materials that are usedto enhance fines settling, the methods and functionalized nanoparticles200 described herein increase the settling rate of tailings fines andcoarse particles while simultaneously removing dissolved metals from thetailings. In some embodiments, a combination of one or more of polydiallyl dimethylammonium chloride or an anionic polyacrylamineflocculent with the functionalized nanoparticles 200 may exhibit animproved removal and settling of fines, coarse particles, and dissolvedmetals.

Additional nonlimiting example embodiments of the disclosure aredescribed below.

Embodiment 1

A method of recovering fines and coarse particles from tailings formedduring recovery of bitumen from oil sands, the method comprising:forming a slurry comprising water and oil sands; separating bitumen fromtailings in at least one of a primary separation vessel or a secondaryseparation vessel, the tailings comprising a solution having fines andcoarse particles suspended therein; mixing functionalized nanoparticleswith the tailings, the functionalized nanoparticles each comprising acore of carbon nitride and functionalized with one or more exposedcationic groups; forming agglomerates comprising the functionalizednanoparticles and at least the fines attached to the one or more exposedcationic groups; and removing the agglomerates from the tailings to forman aqueous solution having suspended therein fewer fines and coarseparticles than are suspended within the tailings.

Embodiment 2

The method of Embodiment 1, further comprising selecting thefunctionalized nanoparticles to comprise a colloidal suspension carbonnitride nanoparticles with one or more exposed cationic groups selectedfrom the group consisting of an amine group, a guanidine group, abiguanidine group, an imidazole group, a pyrazole group, a pyridinegroup, a piperdine group, a pyrrolidine group, a morpholine group, aquinolone group, an isoquinolone group, an indole group, a thiazolegroup, a benzothiazole group, a quaternary ammonium group, a phosphoniumgroup, a sulfonium group, a guanidinium group, a bi-guanidinium group,an imidazolium group, a pyrazolium group, a pyridinium group, apiperidinium group, a morpholinium group, a quinolinium group, anisoquinolinium group, an indolium group, a thiazolium group, abenzothiazonium group, a cyclopropenylium group, an amide group, apolyethyleneimide group, or combinations thereof.

Embodiment 3

The method of Embodiment 2, further comprising adding an acid to thecolloidal suspension and reducing a pH of the colloidal suspension tobetween about 4.0 and about 6.0.

Embodiment 4

The method of any one of Embodiments 1 through 3, further comprisingmixing poly diallyl dimethylammonium chloride with the tailings.

Embodiment 5

The method of Embodiment 4, wherein mixing the poly diallyldimethylammonium chloride with the tailings comprises adding the polydiallyl dimethylammonium chloride to the tailings to achieve aconcentration of between about 50 ppm and about 350 ppm of the polydiallyl dimethylammonium chloride in the tailings.

Embodiment 6

The method of Embodiment 4 or Embodiment 5, further comprising mixingthe poly diallyl dimethylammonium chloride with the tailings aftermixing the functionalized nanoparticles with the tailings.

Embodiment 7

The method of any one of Embodiments 1 through 6, further comprisingrecycling at least a portion of the aqueous solution to at least one ofthe slurry or the primary separation vessel.

Embodiment 8

The method of any one of Embodiments 1 through 7, wherein mixingfunctionalized nanoparticles with the tailings comprises reducing a zetapotential of the tailings to about 0.0 mV.

Embodiment 9

The method of any one of Embodiments 1 through 8, further comprisingadding an anionic polyacrylamine flocculent to the tailings to achieve aconcentration between about 50 ppm and about 350 ppm of the anionicpolyacrylamine flocculent in the tailings.

Embodiment 10

The method of any one of Embodiments 1 through 9, further comprisingselecting the one or more exposed cationic groups to comprise at leastone amine group and one or more a guanidine group, a biguanidine group,an imidazole group, a pyrazole group, a pyridine group, a piperdinegroup, a pyrrolidine group, a morpholine group, a quinolone group, anisoquinolone group, an indole group, a thiazole group, a benzothiazolegroup, a quaternary ammonium group.

Embodiment 11

The method of any one of Embodiments 1 through 10, further comprisingselecting the functionalized nanoparticles to exhibit a zeta potentialhaving an absolute value equal to approximately an absolute value of azeta potential of the fines.

Embodiment 12

The method of any one of Embodiments 1 through 11, wherein mixingfunctionalized nanoparticles with the tailings comprises bindingdissolved metals dissolved in the tailings with functionalizednanoparticles comprising carbon nitride.

Embodiment 13

A method of removing fines from tailings, the method comprising: mixingfunctionalized nanoparticles each comprising at least one exposedfunctional group on surfaces of a carbon nitride core with tailingsincluding negatively charged fine particles to form a mixture, theexposed functional group selected from the group consisting of an aminegroup, an ammonium group, a guanidinium group and derivatives thereof, aphosphonium group, and a sulfonium group; attaching the negativelycharged fine particles to the at least one exposed functional group toform agglomerations of the fine particles attached to the functionalizednanoparticles, the agglomerations having a larger diameter than each ofthe negatively charged fine particles; and separating the agglomerationsfrom the tailings to form a substantially clarified aqueous solutionhaving fewer fines suspended therein than are suspended in the tailings.

Embodiment 14

The method of Embodiment 13, wherein mixing functionalized nanoparticleswith tailings comprises mixing about one functionalized nanoparticle forabout every two negatively charged fine particles in the tailings.

Embodiment 15

The method of Embodiment 13 or Embodiment 14, wherein formingagglomerations of the fine particles attached to the functionalizednanoparticles comprises forming agglomerations having a diameter atleast about five times greater than a diameter of the negatively chargedfine particles.

Embodiment 16

The method of any one of Embodiments 13 through 15, further comprisingadding at least one of an anionic polyacrylamine flocculent or polydiallyl dimethylammonium chloride to the mixture.

Embodiment 17

The method of any one of Embodiments 13 through 16, further comprisingadding functionalized silica nanoparticles to the mixture.

Embodiment 18

A method of separating fines and dissolved metals form tailings, themethod comprising: forming a mixture comprising carbon nitridenanoparticles functionalized with one or more exposed cationic groupsand tailings including a plurality of fines, coarse particles, anddissolved metals suspended therein; binding at least some of thedissolved metals with a core of the carbon nitride nanoparticles;attaching at least some of the fines of the plurality of fines to theone or more exposed cationic groups to form agglomerations of the carbonnitride nanoparticles, bound dissolved metals, and fines; and settlingthe agglomerations from the tailings to form an aqueous solution havingfewer fines, coarse particles, and dissolved metals suspended thereinthan are suspended in the tailings.

Embodiment 19

The method of Embodiment 18, further comprising selecting the exposedcationic groups to comprise amine groups, ammonium groups, guanidiniumgroups and derivatives thereof, phosphonium groups, and sulfoniumgroups.

Embodiment 20

The method of Embodiment 18 or Embodiment 19, further comprising addingpoly diallyl dimethylammonium chloride to the mixture.

While the disclosure is susceptible to various modifications andalternative forms, specific embodiments have been shown by way ofexample in the drawings and have been described in detail herein.However, the disclosure is not intended to be limited to the particularforms disclosed. Rather, the disclosure is to cover all modifications,equivalents, and alternatives falling within the scope of the disclosureas defined by the following appended claims and their legal equivalents.

What is claimed is:
 1. A method of removing at least one of fines,coarse particles, and dissolved metals from tailings, the methodcomprising: mixing tailings with functionalized nanoparticles comprisingat least one exposed functional group on surfaces of a core comprisingcarbon nitride; forming agglomerations comprising the functionalizednanoparticles and at least one of fines, coarse particles, and dissolvedmetals in the tailings; and separating the agglomerations from thetailings.
 2. The method of claim 1, wherein mixing tailings withfunctionalized nanoparticles comprises mixing a colloidal suspensioncomprising functionalized nanoparticles and an acid with the tailings.3. The method of claim 1, wherein forming agglomerations comprising thefunctionalized nanoparticles and at least one of fines, coarseparticles, and dissolved metals in the tailings comprises reducing azeta potential of the tailings to about 0.0 mV.
 4. The method of claim1, further comprising selecting the functionalized nanoparticles toexhibit a zeta potential having an absolute value equal to approximatelyan absolute value of a zeta potential of the at least one of fines,coarse particles, and dissolved metals.
 5. The method of claim 1,further comprising selecting the functionalized nanoparticles to have adiameter between about 5 nm and about 100 nm.
 6. The method of claim 1,wherein mixing tailings with functionalized nanoparticles comprisesmixing the functionalized nanoparticles with the tailings at aconcentration between about 10 ppm and about 1,000 ppm.
 7. The method ofclaim 1, further comprising selecting the at least one exposedfunctional group of the functionalized nanoparticles to comprise exposedcationic groups.
 8. The method of claim 1, further comprising selectingthe at least one exposed functional group of the functionalizednanoparticles to comprise positively charged nitrogen, phosphorus,sulfur, or combinations thereof.
 9. The method of claim 1, furthercomprising selecting the at least one exposed functional group of thefunctionalized nanoparticles to comprise terminal amine groups.
 10. Themethod of claim 1, wherein forming agglomerations comprises bindingmetallic cations from the tailings to the functionalized nanoparticlesto form the agglomerations.
 11. The method of claim 1, wherein mixingtailings with functionalized nanoparticles comprises mixing a powdercomprising the functionalized nanoparticles with the tailings.
 12. Amethod of treating tailings, the method comprising: mixingfunctionalized nanoparticles with tailings to form a mixture comprisingthe tailings and the functionalized nanoparticles, the functionalizednanoparticles comprising at least one exposed functional group onsurfaces of a core comprising at least one of carbon nitride,nanodiamond, a metal carbide, a metal phosphate, a metal sulfide, ornitrides of iron, tin, lead, ruthenium, nickel or cobalt; formingagglomerations comprising the functionalized nanoparticles and at leastone of dissolved metals, fines, and coarse particles; and removing theagglomerations from the mixture to form an aqueous solution.
 13. Themethod of claim 12, further comprising providing at least a portion ofthe aqueous solution to at least one of a primary separation vessel anda secondary recovery vessel.
 14. The method of claim 12, furthercomprising selecting the core to comprise carbon nitride.
 15. The methodof claim 12, further comprising selecting the at least one exposedfunctional group of the functionalized nanoparticles to comprise exposedcationic groups selected from the group consisting of amine groups,ammonium groups, gadolinium groups, phosphonium groups, and sulfoniumgroups.
 16. A mixture for removing fines and coarse particles fromtailings, the mixture comprising: tailings including fines and coarseparticles; and functionalized nanoparticles formulated and configured tointeract with one or more of the fines, the coarse particles, anddissolved metals in the tailings, the functionalized nanoparticlescomprising: at least one exposed functional group on surfaces of a corecomprising carbon nitride.
 17. The mixture of claim 16, wherein the atleast one exposed functional group of the functionalized nanoparticlescomprises exposed cationic groups.
 18. The mixture of claim 16, whereinthe at least one exposed functional group of the functionalizednanoparticles comprises positively charged nitrogen, phosphorus, sulfur,or combinations thereof.